With the development of a wireless communication technology, a demand for a large capacity data service such as a multimedia service from users is increasing. Thus, an Orthogonal Frequency Division Multiplexing (OFDM) transmission scheme enabling provision of a large capacity data service at a high speed has been highlighted.
If using the OFDM transmission scheme, a wireless communication system transmits one data stream through a plurality of subcarriers. In the wireless communication system of the OFDM transmission scheme, a high Peak to Average Power Ratio (PAPR) is generated by the plurality of subcarriers.
To reduce a high PAPR caused by the OFDM transmission scheme, an SC transmission scheme has been proposed. That is, if using the SC transmission scheme, a wireless communication system transmits one data stream through one carrier and thus, low PAPR performance is generated.
The wireless communication system of the SC transmission scheme can additionally use a multiple antenna technology to maximize transmission performance. In this case, the wireless communication system of the SC transmission scheme has an advantage of maintaining the merits of the SC transmission scheme while being capable of achieving diversity gain and space multiplexing gain by the multiple antenna technology.
To enhance reception performance, a multiple antenna system uses an ML scheme. If using the ML scheme, a receive end determines Euclidian distances between all candidate transmission symbols that a transmit end can transmit and a receive signal. After that, the receive end selects a candidate transmission symbol having the shortest Euclidean distance as a symbol of the receive signal.
If a multiple antenna system of an SC transmission scheme uses an ML scheme, a receive end detects a receive signal by applying the ML scheme in a time domain. That is, a signal that the receive end receives through an nth time resource includes, by multipath fading, not only a signal that a transmit end transmits through the nth time resource but also a signal that the transmit end transmits through a previous time resource. Thus, the receive end determines Euclidean distances between not only all candidate transmission symbol vectors that the transmit end can transmit through the nth time resource but also all candidate transmission symbol vectors that the transmit end can transmit through the previous time resource, and a signal that the receive end itself receives through the nth time resource.
After that, the receive end selects a candidate transmission symbol having the shortest Euclidean distance as a symbol of the signal received through the nth time resource.
As described above, if a multiple antenna system using an SC transmission scheme uses an ML scheme, a receive end has to consider even candidate transmission symbol vectors that a transmit end can transmit through a previous time resource. Thus, there is a problem that the complexity of the receive end increases if the multiple antenna system using the SC transmission scheme uses the ML scheme.